1. Field of the Invention
The invention relates to an optical touch system and a touch display system using the optical touch system.
2. Description of the Prior Art
Some optical touch systems use light sensing devices disposed at the border of a touch area to capture touch signals relative to the touch area so as to determine the touch position of an object (e.g. a finger or touch pen). However, the disposition (including a relative position and a lens angle) of the light sensing device relative to the touch area may involve a variation due to the assembly of the light sensing device (e.g. assembled onto a liquid crystal display panel) or the system setup before use (e.g. for a projection displaying system), so before the usage of touch function, it is necessary to perform a calibration procedure so that the range of touch signals sensed by the light sensing devices can correctly correspond to the range of the touch area when the sensed touch signals are analyzed. The calibration procedure usually needs reference touches (e.g. at the four corners of the touch area) by a user. However, human actions will involve variation, so even after the calibration procedure, a little variation still exists in the corresponding relation of the range of the touch signals sensed by the light sensing devices to the range of the touch area. Furthermore, when several light sensing devices are used, relative distances among the light sensing devices are needed for determining more precise coordinates of a touch. For simplifying the analysis, the distances are set to be a fixed value. However, in projection displaying systems, the touch area thereof often varies on actual use situations (e.g. for different projection areas), leading to a difficulty in applying the above design of fixed distance.